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const arr = [1, 2, 1, 2, 3, 3, 4, 5]

arr.filter((e, i) => arr.indexOf(e) !== i)
// returns [1, 2, 3]

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map = (fn, [head, ...tail]) => 
  (head === undefined && tail.length < 1)
    ? []
    : [fn(head), ...map(fn, tail)]

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// https://medium.com/javascript-in-plain-english/how-to-deep-copy-objects-and-arrays-in-javascript-7c911359b089

JSON.parse(JSON.stringify(...))

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const fibonacci = n =>
  [...Array(n)].reduce(
    (acc, val, i) => acc.concat( // concat returns the new acc
      i > 1
        ? acc[i - 1] + acc[i - 2]
        : i
    ),
    []
  )

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val tolerance = 0.00001

def isCloseEnough(x: Double, y: Double): Boolean =
  Math.abs((x - y) / x) / x < tolerance

def fixedPoint(f: Double => Double)(firstGuess: Double) = {

  def iterate(guess: Double): Double = {
    val next = f(guess)
    if (isCloseEnough(guess, next))

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import scala.annotation.tailrec

def recursiveSum(f: Int => Int)(a: Int, b: Int): Int = {
  if (a > b)
    0
  else
    f(a) + recursiveSum(f)(a + 1, b)
}

def tailRecursiveSum(f: Int => Int)(a: Int, b: Int): Int = {

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const seconds = time => time // formatted as 'HH:MM:SS'
  .split(':')
  .reverse()
  .reduce((acc, val, i) => acc + val * 60 ** i, 0)

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const filename = pathname.replace(/^.*[\\\/]/g, '')

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const { ApolloServer, gql } = require('apollo-server')

// The GraphQL schema
const typeDefs = gql`
  type Query {
    "A simple type for getting started!"
    foo: String
    foofoo: Int
  }
`

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/**
 * 
 * @param {string} text
 * 
 * Return a plain JS object providing the number of occurrences of every word containing at least 3 characters from the text 
 */
const wordOccurrences = (text) => { // functional programming version
  return text
    .split(' ')
    .filter((token) => token.length > 2)